NFPA 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment
NFPA 496 電氣設備的氣體保護標準
1.1 Scope.
1.1.1 This standard applies to purging and pressurizing for the following
(1) Electrical equipment located in areas classified as hazardous by Article 500 or Article 505 of NFPA 70
(2) Electrical equipment containing sources of flammable vapors or gases and located in either classified or unclassified areas
(3) Control rooms or buildings located in areas classified as hazardous by Article 500 or Article 505 of NFPA 70
(4) Analyzer rooms containing sources of flammable vapors or gases and located in areas classified as hazardous by Article 500 or Article 505 of NFPA 70
1.1.2* This standard does not apply to electrical equipment located in
(1) Areas classified as Class I, Zone 0
(2) Areas classified as Class III
(3) Areas where flammable liquids may be splashed or spilled on the electrical equipment.
Protect electrical equipment in flammable atmospheres by following the protection techniques outlined in the 2008 NFPA 496.
NFPA 496 Purged and Pressurized Enclosures for Electrical Equipment contains requirements for the design and operation of purged and pressurized electrical equipment enclosures. This protection technique is used in Class I and Class II hazardous (classified) locations to reduce or prevent the presence of flammable materials within electrical equipment enclosures as specified by NFPA 70® National Electrical Code®. NFPA 496 also includes chapters covering protection of analyzers and rooms housing analyzers as well as a chapter on pressurized control rooms.
Consistent with the 2008 NEC®, the 2008 NFPA 496 includes the following updates to help control fire hazards
· A new requirement to mark purged and pressurized enclosures with an asphyxiation hazard warning where the protective gas is other than air
· Correlation with the NEC requirements on equipment temperature ratings
(Softbound, 22 pp., 2008)
